Fecal occult blood testing has become a popular, widely used procedure useful in the detection of relatively small amounts of blood in fecal specimens. This wide use and popularity arises primarily because fecal occult blood testing is non-invasive, simple and inexpensive to perform. Because the presence of fecal occult blood in a specimen is a symptom that may be associated with colon cancer or a precursor to colon cancer, fecal occult blood testing is often routinely used as a screening tool. The routine screening of patients by means of fecal occult blood testing has helped to detect colon cancer at a stage where the disease is readily treatable.
A popular form of fecal occult blood testing utilizes a guaiac treated test sheet where a fecal material specimen is smeared on a front, or, "test material placement" side of the test sheet. The fecal material has a tendency to diffuse through the test sheet, defining a region on a side of the sheet opposite to the test material placement side. The portion of the sheet opposite to where the test material is smeared is the back, or, "developing" side of the sheet, and the area on the developing side of the test sheet where the fecal material diffuses through from the test material placement side of the test sheet is referred to herein as the "diffused region" or the "diffused area". A developing solution is applied to the developing side of the sheet directly onto the diffused region, and if a color change is indicated, blood may be present in the fecal specimen.
There has been an on-going need to obtain, transport and process the specimens of the fecal occult blood test in a manner that is as convenient and as aesthetically acceptable as possible. One form of specimen collection device that has gained wide popularity is a slide formed from folded paper or cardboard. The slide includes guaiac treated paper to which the fecal specimen is applied through a "test window" or "aperture" located on the test material placement side of the test sheet, and a cover which is closed once the specimen application is completed. A flap in the back of the slide may be opened to reveal the developing side of the guaiac treated paper for subsequent application of developer onto an area of the developing side of the test sheet directly opposite to the aperture or apertures, i.e., directly onto the diffused region. A positive result, that is, one indicating the presence of blood in the fecal sample, is determined by the presence of (usually) a blue color, and the intensity thereof provides further information as to the amount of blood present in the fecal sample.
Specimen slides for fecal occult blood tests generally have test windows of varying sizes. In an attempt to standardize the sample amount applied through the test windows and in an effort to mitigate against over- or under- application of sample, instructions for sample application are ordinarily provided to the patient. These instructions vary, but are generally intended to provide direction to the patient in an effort to limit the amount of sample smeared into the test window, i.e., "apply a thin smear"; "a pea size"; or "the size of a match head". The quantity of the sample on the slides returned to the laboratory varies from trace amounts, which are insufficient for proper testing, to very excessive amounts, which also create technical, as well as aesthetic, problems. It is often the case that when there is too much sample on the test material placement side, the developing side of the slide is fully covered with the colored stain of the diffused sample. This makes reading of test results based on color intensity difficult and usually impossible.
Errors on the part of the technician developing the test slide may also occur. For example, if the technician inadvertently adds developer to the test material placement side of the test slide, as opposed to the developing side, the sample can be flooded with the developing solution, leading to incomprehensible, incorrect or misleading results, due to reconstitution of the sample. Furthermore, the instructions for application of the developing solutions require application thereof directly onto the diffused region. It is often the case, particularly when an insufficient amount of sample is present, that far too much developing solution will be added directly onto this area in an attempt to compensate for the lack of sufficient sample. This also has the effect of flooding the diffused region, which can result in incomprehensible, incorrect or misleading results, i.e. the intensity of the color can be artificially altered.
Most of the problems associated with differing amounts of sample added to the test slide by the patient are predicted upon the inexperience of the patient with such test slides. Given the very nature of, for example, fecal sample materials, different individuals will react differently to applying such a sample to a test slide. Therefore, while instructions can be provided to the patient as to how much of a sample should be placed in the test window area, consistent amounts of sample across of wide-ranging group of patients are not obtainable, as experience has demonstrated. Additionally, the technician who attempts to develop a test on a test slide that includes either inadequate or excessive amounts of sample could possibly provide incorrect results to the patient or the patient's physician; thus the medical technician who attempts, albeit incorrectly, to compensate for incorrect sample amounts could possibly provide the patient or the patient's physician with results that do not lead to additional (and necessary) tests, or with results that lead to additional (but unnecessary) tests. Thus, the technician who provides such erroneous results could be exposed to legal liability.
Because the performance of the test is dependent on the reproducibility, ease of use by patients, as well as efficient, yet simple, sampling/developing procedures, an improved specimen test slide taking the above factors into account is not only desirable, but necessary.